U.S. patent application number 10/519181 was filed with the patent office on 2006-05-11 for laser beam homogenisers in medical applications.
Invention is credited to Richard Walmsley.
Application Number | 20060100676 10/519181 |
Document ID | / |
Family ID | 3836698 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060100676 |
Kind Code |
A1 |
Walmsley; Richard |
May 11, 2006 |
Laser beam homogenisers in medical applications
Abstract
A device is disclosed usable for low level laser therapy to
induce a photochemical reaction (non-heating) which is used in the
treatment of conditions like tendonitis and other soft tissue
injuries, wound healing and pain relief. The arrangement proposed
will allow the device to be a Class I laser device thus providing
long term minimization of the running costs of the device. The
device includes a laser generating means (10) for generating a
laser beam (14), the laser generating means (10) having an apparent
source size and homogenising means (12) for modifying the laser
beam (14) for modifying the apparent source size of the laser beam
(14).
Inventors: |
Walmsley; Richard; (South
Yarra, AU) |
Correspondence
Address: |
CALFEE HALTER & GRISWOLD, LLP
800 SUPERIOR AVENUE
SUITE 1400
CLEVELAND
OH
44114
US
|
Family ID: |
3836698 |
Appl. No.: |
10/519181 |
Filed: |
June 25, 2003 |
PCT Filed: |
June 25, 2003 |
PCT NO: |
PCT/AU03/00791 |
371 Date: |
October 6, 2005 |
Current U.S.
Class: |
607/89 |
Current CPC
Class: |
A61N 2005/067 20130101;
A61B 2018/2261 20130101; A61N 2005/0644 20130101; A61N 5/0616
20130101 |
Class at
Publication: |
607/089 |
International
Class: |
A61N 5/06 20060101
A61N005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 25, 2002 |
AU |
PS 3138 |
Claims
1. A device for a medical diagnostic or therapeutic purpose, said
device including: laser generating means for generating a laser
beam, said laser generating means having an apparent source size;
homogenising means for modifying said laser beam; wherein said
modifying adjusts the apparent source size of said laser beam.
2. A device as claimed in claim 1, wherein said homogenising means
further modifies a spot size of said laser beam.
3. A device as claimed in claim 1, wherein said apparent source
size of said laser beam is greater than that required as a minimum
condition for classification of said device as a Class I laser.
4. A device as claimed in claim 1, wherein said laser generating
means includes a laser emitting diode.
5. A device as claimed in claim 1, wherein said homogenizing means
includes an optical homogeniser.
6. A device as claimed in claim 5, wherein said optical homogeniser
includes a microlens array.
7. A device as claimed in claim 5, wherein said optical homogeniser
includes a holographic diffuser.
8. A device as claimed in claim 1, where said medical diagnostic or
therapeutic purpose is the treatment of conditions ameliorated by
photochemical low level laser therapy.
9. A device as claimed in claim 1 wherein said medical diagnostic
or therapeutic process is the treatment of lymphodema.
10. A device as claimed in claim 1 further including a positioning
means for positioning said device at a predetermined distance and
orientation from a surface according to a requirement of said
medical purpose.
11. A device as claimed in claim 10, wherein said positioning means
includes a frame, said frame adjustably attached to said device and
when in use for a medical diagnostic or therapeutic purpose
providing an abutment surface relative to said treatment area.
12. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates to laser systems and in particular to
Lasers used in the medical field.
BACKGROUND OF THE INVENTION
[0002] Safety when using or being exposed to lasers is a very
important consideration International Standards exist with regards
to the classification of laser devices and the way in which
different classes of laser can be used. Those laser devices that
conform to the laser safety Class I definition (ie IEC825-1,
AS2211) are considered the safest.
[0003] Laser emitting devices that do not fall within the Class I
definition require the device and the user, and in medical
applications the patient to use or be subject to one or more of the
following: use of safety spectacles, interlock systems, warning
lights, etc.
[0004] Laser emitting devices have a wide range of wavelength,
energy and pulse characteristics and the classification system is a
guide as to the way in which each device having one or more of
those characteristics can be used and by whom the device can be
used.
[0005] A Class I laser-emitting device can be used without
restriction but in accordance with the manufacturer's instructions
for the purpose for which it was designed. This means that special
training and additional safety equipment is not required. Thus
operating costs are less when compared to the attendant operating
costs of other classes of laser-emitting devices.
[0006] A major consideration when designing laser-emitting devices
is the amount of power that the source laser in the device is
required to emit so as to provide adequate laser emission power
from the laser device. One of the determinants of this
characteristic is the required power density to be delivered at the
application site over a desired area.
[0007] As the area required to be treated increases for a required
power density so does the power of the source laser needed to
support that requirement.
[0008] Apart from the power, pulse parameters and wavelength of the
laser, another of the critical features in specifying the class of
the laser is the apparent aperture of the laser source. The
apparent aperture will determine the image size that the laser
source can form for example on the retina of an inadvertent
observer.
[0009] The requirement described above is sometimes referred to as
the apparent source and it is this characteristic that is used to
determine the class of the laser emitting device.
[0010] Current laser device configurations are restricted somewhat
by the physics of the devices used to generate the source laser.
For diode laser sources, the emitting aperture (the area of the
spot beam) of the laser radiation is typically 7.times.1 microns
for a 904 nanometer Gallium Arsenide (Ga--As) laser diode. These
devices typically have pulsed outputs with 1 and 5 Watt peak powers
with the pulse repetition and duration being variable to suit the
application. There are many other laser diode configurations, the
device type described above is an example of such devices.
[0011] In some applications it is desired to not only provide the
laser radiation over a larger area but also to control the power
density thus requiring an adequately high power laser source.
[0012] It is an aim of the invention described herein to provide a
laser emitting device that meets not only a desired power density
and spot area requirement, but that meets Class I requirements thus
providing long term minimization of the running costs of the
device.
SUMMARY OF THE INVENTION
[0013] Accordingly the present invention provides a device for a
medical diagnostic or therapeutic purpose, said device including:
[0014] laser generating means for generating a laser beam, said
laser generating means having an apparent source size; [0015]
homogenising means for modifying said laser beam; [0016] wherein
said modifying adjusts the apparent source size of said laser
beam.
[0017] Preferably the homogenising means further modifies a spot
size of said laser beam.
[0018] Preferably the apparent source size of said laser beam is
greater than that required as a minimum condition for
classification of said device as a Class I laser.
[0019] Preferably the homogenizing means includes an optical
homogeniser.
[0020] Preferably the optical homogeniser includes a microlens
array.
[0021] Optionally the optical homogeniser includes a holographic
diffuser.
[0022] Preferably the device further includes positioning means for
positioning said device at a predetermined distance and orientation
from a surface according to a requirement of said medical
purpose.
BRIEF DESCRIPTION OF THE FIGURES
[0023] Specific embodiments of the invention will now be described
in some further detail with reference to and as illustrated in the
accompanying figures. These embodiments are illustrative, and not
meant to be restrictive of the scope of the invention. Suggestions
and descriptions of other embodiments may be included within the
scope of the invention but they may not be illustrated in the
accompanying figures or alternatively features of the invention may
be shown in the figures but not described in the specification.
[0024] FIG. 1 depicts use of a preferred embodiment of the
invention for the treatment of lymphodeama; and
[0025] FIG. 2 depicts a generic arrangement of a preferred
laser-emitting device according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0026] Although a particular medical application is described
herein and a particular laser emitting device configuration is also
described, it should be understood that these details are
illustrative only and not meant to be limiting in any way upon the
application or configuration of the principle of the invention.
[0027] In the medical field, low power level laser radiation is
known to have beneficial medical effects in some disease and
restorative therapies.
[0028] One example is the treatment of lymphoedema other examples
include use of low level laser therapy to induce a photochemical
reaction (non-heating) which is used in the treatment of conditions
like tendonitis and other soft tissue injuries, wound healing and
pain relief.
[0029] Clearly, the frequency, power level (continuously on or
modulated on/off duty cycle of the radiation at the same or
changing levels) and characteristics of the laser are determined by
the nature of the treatment outcome desired by a clinician.
[0030] The area of effective laser irradiation on the relevant
tissue or organ of the patient is a matter of design and
specification by the clinician.
[0031] Laser source emitting 600-1000 nanometers wavelength at 1 mW
to 1 W power can be used. Such devices are usually class IIIB but
by using the invention described herein will become Class 1.
[0032] In a preferred arrangement the laser source is a Galium
Arsenide Laser diode having an emitting aperture of 7.times.1
microns of 904 nanometer wavelength having 5-Watts peak power. In a
lymphoedema application such as depicted in FIG. 2, the laser
output is modulated or controlled to have a low 2,500 Hz and high
5,000 Hz repetition rate of 200-nanosecond duration. Such a device
falls near the Class I and adjacent Class IIIB boundary.
[0033] As shown in FIG. 1, in this type of medical procedure the
operator holds the treatment device 20 incorporating the laser
emitting device 10 so that the apparent aperture is moved in a
predetermined path over the patient's treatment area. The treatment
area is usually the tissue in near vicinity of the potentially or
actually diseased lymph nodes, under the patients arm (as shown) or
the groin area are examples of treatment sites. The treatment
device 20 may include a plastic or metal frame 18 that has an
abutment surface that is positioned on the treatment area to be
irradiated whilst the other end is fixed relative to treatment
device 20.
[0034] There is exists a slight divergence of the laser beam which
is factored into the design, the amount of divergence being
directly proportional to the distance between the output aperture
of the laser diode and the patient's treatment site.
[0035] The invention includes the use of an optical homogeniser
such as for example a CORNING.TM. high performance microlens array.
A specification of its characteristics includes that it is made
from either fused silica, silicon or polymer-on-silica. It has a
center to center spacing tolerance of less than 1 micrometer and a
total run-out over 50 mm of less than 7 micrometers. It has a
maximum array size of 50 mm by 50 mm, a maximum substrate diameter
of 150 mm and minimum substrate thickness of 400 micrometers.
[0036] Characteristics of the microlens are as follows. It can be
spherical or aspherical and is designed with a polymer surface
irregularity less than one quarter of a wavelength at 633
nanometers. For the silicon oxide (SiO.sub.2) variety at least 97%
of the lens surface has a surface irregularity of less than one
half of a wavelength at 633 nanometers.
[0037] The focal length for a microlens can be designed to vary
between 1.5 mm and 6.0 mm at wavelengths greater than or equal to
200 micrometers. The focal length tolerance in air for a polymer
microlens is plus or minus 10 micrometers within the array and plus
or minus 25 micrometers when measured array to array. For a
SiO.sub.2 array the focal length tolerance in air is plus or minus
50 micrometers within the array and plus or minus 50 micrometers
when measured array to array.
[0038] Clear aperture dimension is less than or equal to 1.3 mm and
surface roughness is less than 100 Angstroms .ANG. (Ra). The
operating temperature is permitted to be between 0 and 70.degree.
C.
[0039] The surface relief diffuser version of the microlens array
is used in preferred arrangements that are designed to spread light
in a predetermined gain distribution Both symmetric and asymmetric
surface relief diffusers can be used dependent on the application.
This is not the only type of homogeniser that can be used, there
are other fabrication techniques such as holographic diffusers. The
important aspect is that the homogeniser acts like a near perfect
diffuser thus causing the apparent aperture to be the homogeniser
not the aperture of the emitting device.
[0040] In the subject application the apparent aperture of the
source laser device is made uniformly larger to the order of 6
mm.sup.2.
[0041] The preferred distance between the laser source aperture and
the optical homogeniser is 5 mm. This accounts for the divergence
of the source laser beam and as a result the apparent aperture and
power distribution is such that the full device falls well within
Class I limits.
[0042] FIG. 2 displays the laser source 10 and a homogeniser
element 12 located a distance D1 from the laser source. The
slightly divergent laser beam 14 from the source is exaggerated for
the purpose of illustration only. The resultant laser beam power
distribution is pictorially shown at 16 a distance D2 from the
homogeniser element.
[0043] Having the arrangement described allows for the power output
of the source laser to be increased allowing the ideal required
power distribution to be homogeneously distributed over a much
greater area than would otherwise be the case. This in turn allows
the total Laser-radiating device to remain within the Class I laser
classification. This ultimately reduces cost to the patient.
[0044] A larger area can be treated at the same time, thus reducing
treatment time and complexity of movement This further benefits the
patient, as the period of potential discomfort is minimized.
[0045] It will be appreciated by those skilled in the art that the
invention is not restricted in its use to the particular
application described. Neither is the present invention restricted
in its preferred embodiment with regard to the particular elements
and/or features described or depicted herein. It will be
appreciated that various modifications can be made without
departing from the principles of the invention. Therefore, the
invention should be understood to include all such modifications
within its scope.
* * * * *